• 센서학회지
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• 제16권4호
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• pp.263-269
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• 2007

Although variable resistance displacement transducer is widely applied for its technical simplicity, electrical point contact limits measurement resolution (precision). The present study introduced roller shaped structure for electrical line contact. Proto-type transducer was developed and measurement characteristics were compared with a commercialized product. When the displacement was varied with steps of 5 mm, 1 mm, and down to 0.1 mm, the correlation coefficient between resistance and displacement decreased lower than 0.9 in the commercialized product while the proto-type transducer maintained values higher than 0.99. Therefore, the measurement resolution was enhanced by approximately 10 times. Since manufacturing also seemed easier, the present results would enable more accurate and less expensive manufacturing of variable resistance displacement transducer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.864-868
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• 2005

This paper develops an analysis model of a piezoelectric transducer. The transducer considered in this paper is a bolt-clamped Langevin-type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analytical model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic and the metal block. The analysis model is verified by calculating the variations of the resonance frequency due to the contact area and comparing them with reported experimental results.

• Journal of Biosystems Engineering
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• 제38권3호
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• pp.192-198
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• 2013

Purpose: Methods for non-destructive estimation of product quality have been reported in various industrial fields, but the application of ultrasonic techniques for the agricultural products of potatoes, pears, apples, watermelons, kiwis and tomatoes etc. have been rarely reported since the application of a contact-type ultrasonic transducer in agricultural products is very difficult. Therefore, this study sought to determine the firmness of apples using non-contact ultrasonic techniques. Methods: For this experiment, an ultrasonic experimental tester using a non-contact ultrasonic transducer was created, and a signal processing program was used to analyze the acquired ultrasonic reflected signal. Also, a universal testing machine was used to measure firmness parameters of the apples such as bioyield strength, a firmness factor, after the ultrasonic tests had been performed. Results: Six distance correction factors were calculated to obtain consistent values of ultrasonic properties regardless of the distance between the transducer and the surface of the subject. We developed prediction models of the bioyield strength using the distance correction factors. Conclusions: The optimum prediction model of the bioyield strength of apples using a non-contact ultrasonic technique was a multiple regression model ($R^2=0.9402$).

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.46-52
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• 2019

This work proposes a noncontact ultrasonic transducer for detecting wall-thinning of containment liner plates of nuclear power plants by measuring their thickness without physical contact. Because the containment liner plate is designed to prevent atmospheric leakage of radioactive substances under severe nuclear accident, its wall-thinning inspection is important for safety of nuclear power plants. Wall-thinning investigation of containment liner plates have been carried out by measuring their thickness with contact-type ultrasonic thickness gauge by inspectors and needs a lot of time and cost. As an alternative, an electromagnetic acoustic transducer measuring precisely thickness of containment liner plates without any physical contact or couplant was suggested in this research. A transducer generating and measuring shear ultrasonic waves in thickness direction was designed and wave field produced by the transducer was analyzed to verify the design. The working performance of the suggested transducer was tested with carbon steel plate specimens with various thicknesses. The test result shows that the proposed transducer can measure thickness of the specimens precisely without any couplant and implies that swift scanning of wall-thinning of containment liner plates will be possible with the proposed transducer.

• 보존과학회지
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• 제31권3호
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• pp.267-278
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• 2015

이 연구에서는 석조문화유산의 표면 요철도를 고려한 맞춤형 초음파 측정법을 설정하기 위해 새로운 접촉매질인 엘라스토머 커버를 개발하였다. 이 커버는 17MPa의 인장강도와 625%의 신장도를 가져 탄성력이 매우 우수하고 마모되지 않는 특징이 있다. 또한 엘라스토머 커버를 포함하여 탐촉자 및 접촉매질에 따른 7개 유형의 비교 실험 결과, 암석의 표면 거칠기는 초음파속도 감쇠에 많은 영향을 끼쳤다. 이러한 현상은 잔다듬에서 정다듬으로 갈수록, 직접전달방법보다는 간접전달방법에서 두드러졌다. 그러나 지수형 탐촉자와 엘라스토머 커버를 사용하는 유형 F는 요철도에 큰 상관없이 안정된 초음파속도와 높은 첨두치를 나타냈다. 이는 접촉매질로 사용한 엘라스토머 커버가 요철 표면에 충분히 밀착되어 탐촉자와 시편 사이의 공극을 제거했기 때문이다. 따라서 석조문화유산의 초음파 측정은 유형 F를 사용하는 것이 가장 적합할 것으로 판단된다.

• 비파괴검사학회지
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• 제28권4호
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• pp.358-363
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• 2008

재료의 미세열화를 측정하는 비파괴검사법으로 초음파의 비선형파라미터 측정기법이 최근 주목받고 있다. 하지만 그 크기가 매우 작기 때문에 여러 측정 인자들로부터 영향을 받아 일관성 있는 측정이 어렵다. 따라서 본 연구에서는 접촉식 탐촉자를 이용한 초음파 비선형파라미터의 측정에서 측정시스템에 의존하는 인자들의 영향을 연구하였다. 그 결과 탐촉자 접촉압력과 인가전압이 충분히 클수록 시스템 비선형성의 영향을 줄일 수 있음을 알 수 있었다. 이 연구의 결과는 정확한 비선형파라미터의 측정을 위한 실험조건을 설정하는 방법으로서 유용하게 사용될 것이 기대된다.

• 한국소음진동공학회논문집
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• 제16권1호
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• pp.89-100
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• 2006

This paper presents an analytical approach to describe the variation in the vibration characteristics such as the natural frequency of a piezoelectric transducer under static pre-pressure. The transducer considered in this paper is a bolt-clamped Langevin-type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analysis model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic disc and the metal block. The variation of the resonance frequency due to the pre-pressure has been calculated and compared with measured results reported earlier.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.484-487
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• 2005

This paper presents an analytical approach to describe the variation in the vibration characteristics such as the natural frequency of a piezoelectric transducer under static pre-pressure. The transducer considered in this paper is a bolt clamped Langevin type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analysis model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic and the metal block. The variation of the resonance frequency due to the pre-pressure has been calculated compared with other results.

• 한국정밀공학회지
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• 제19권3호
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• pp.39-45
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• 2002

A simple and low cost stylus profiler made of ferrite cores is developed. The devised profiler consists of a contact probe, a measuring transducer, a signal processing unit, and a motorized stage. The contact probe attached to 4-bar spring maintains sufficient stiffness to protect disturbances. An overlap-area type inductive position sensing system is selected as a measuring transducer, which has high sensitivity, repeatability and linearity. The transducer is composed of coil bundles and ferrite cores which have good electromagnetic characteristics in spite of low cost. The repeatability of the profiler with the proposed inductive sensing system is better than 50nm. Experimental results are shown that the proposed profiler can measure the line or 3D profile of an object with sub-micron features.

• 보존과학회지
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• 제25권3호
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• pp.233-244
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• 2009

이 연구에서는 석조문화재의 초음파 측정에 적합한 탐촉자 및 접촉매질을 선정하였으며, 과학적이며 정량적인 평가기술을 개발하기 위해 암종별 직접 및 간접전달방법의 상관관계를 분석하였다. 이 결과, 석조문화재에서 초음파 측정은 유형 3의 탐촉자(UTREXTX(RX)54kHz)와 접촉매질(고무찰흙)을 사용하는 것이 가장 적합한 것으로 나타났다. 또한 이 유형 3의 직접 및 간접전달방법의 보정계수는 화강암 1.50, 반려암 1.38, 석영섬록암 1.58로 산출되었다. 이 결과는 초음파탐사의 신뢰도를 높이기 위한 최초의 연구로서 석조문화재의 초음파탐사 방법을 확립하는데 크게 기여할 것으로 판단된다. 또한 암석의 표면요철도와 다양한 접촉매질을 고려한 보완연구가 수행되어야 할 것이며, 암종별 직접-간접전달방법의 상관관계에 대한 데이터베이스도 구축되어야 할 것이다.